Tuesday, November 14, 2006

Aflatoxin B1 Sorption in Smectite Clays versus pH.

Maria Guadalupe Tenorio Arvide, Ines Kannewischer, and Joe B. Dixon. Texas A&M Univ, 370 Olsen Blvd, College Station, TX 77843-2474

Aflatoxicosis in animals and potentially liver cancer in humans can be caused by ingestion of diets contaminated with mycotoxins particularly aflatoxin B1 (AfB1), a serious environmental hazard. In spite of the great amount of research toward preventing aflatoxin in grains, it continues to be produced under stressful climatic conditions. A practical approach is required for immediate relief and the use of smectite clay sorbents has been successful. Yet the mechanism of sorption is not well understood. The objective in this study was to determinate the sorption of AfB1 by smectite clays with different pHs. The samples were screened for their physical and chemical properties, AfB1 sorption capacity, and its influence on their properties as measured by XRD features. The results are focused on 3 representative samples: 17TX pH=4.7; 8TX pH=7.1; and 6WY pH=9.6. The average exchange properties are: C.E.C 81.0; K=1.0; and Mg=19 cmol/kg. For the three clays exchangeable Ca was: 36.8, 54.6, and 15.5 cmol/kg and exchangeable Na: 10.7, 8.3 and 83.6 cmol/kg, respectively. The AfB1 sorption capacity values in mol/kg were:  0.37 for 17TX; 0.67 for 8TX and 0.29 for 6WY. The XRD patterns showed smectite peak. Sample 6WY is consistent with our other samples high in Na and low in AfB1 sorption. We speculate that the low AfB1 sorption capacity may be caused by greater particle dispersion of Na and increased layer separation in water. The other two samples did not follow this relationship. The reason for low sorption by 17TX may be the presence of interlayer Al, suggested by the extreme acidity.  A near neutral pH is usually associated with high AfB1 sorption, but there are exceptions.

Handout (.pdf format, 1049.0 kb)